Sputnik

It depends on the setup, frankly. Some setups that have severe lag because of an over-sized turbo will be harder to get used to, and more limited in response time, but it's all in the way you drive it. A well designed and setup turbo system will not have such a sudden onrush of power, and it's no harder to control than a high-power NA or SC car. You just have to get used to it like any other new car that you get into.

---jps

N1XRR

You know, not ALL turbo's are slow to spool. A ball-bearing turbo spools almost instantly, and can produce boost all the way up to redline....trust me, I've rode in an FC with a ball-bearing turbo, full boost at 1700rpms, and 15psi....reliable too

Michael

wakeech

uh, i'm pretty sure that any modern turbo is running on ball-bearings... i wouldn't dare think of something running 20 000 rpm on freakin' roller bearings, although i'm sure it's been done
and a turbo that's makin' only 15 psi of boost doesn't have to be enourmous...
what the deal is with the lag, is when you're at idle, and you mash the pedal to go, there's a gap in the power... you go, but then some short amount of time later, you get a whack to the back of the head from your seat as the power surges on...
if you're already moving, and cruising at 1500 rpm, the turbine is already spinning at a good speed, and thus doesn't need to be accelerated nearly as much, so the lag is quite minimal...
the reason that big turbos have more lag than small ones is all becuase of their mass: i can't remember the equation, but obviously, the more mass you've got, the slower it's gonna accelerate for any given amount of force...
so, ya, your buddie's turbo FC (man i love that car... ) wouldn't seem like it has enourmous amounts of lag, but something like a twin turbo drag car running upwards of 35 or 40 lb. of boost (i've heard of higher... like in the old school can am cars... porshe's twin turbo v12?? i can't remember how much boost, but the driver described the power surge "like being hit in the back of the head with a [baseball] bat") would obviously suffer from considerable lag, even when they're dropping the clutch from 5k RPM... i'm sure you've seen this if you've watched, say, a muscle car go up against a fat turbo I6... the muscle car launches away, and the Supra (which was what i saw...) looked like it was walking, even though it hit the redline... in second gear, that bloody Supra blew the shiznat outa the V8, and won out by like .4 in the end, or something (this was some crazy drag racing class, semi-professional stuff, at some strip, somewhere, on some tv channel, a long time ago... useful only for example...)

Sputnik

Even nowadays, a ball-bearing turbo is not the norm, per se. So you can't assume that it a particular turbo will be ball-bearing. BTW, ball bearing is pretty much the same as roller bearing. A "non-ball-bearing" turbo is a sleeve bearing, and street turbos can spin up to 100,000 rpm.

---jps

N1XRR

Thank you. I believe there are only 4 cars on the road which are ball-bearing turbo's(stock anyway, as of 4 years ago). Sleeve bearings tend to have a lot of friction, which causes slow spool and lower boost than compared to a ball-bearing type. 100,000rpm's+. DSM's stock run about 110000rpms at full boost, with boost controller and BOV upgrades they can go up to 140,000rpms.

There's so much friction that a larger turbo can spool faster than a smaller turbo, provide more boost, and last longer than the old style. Result, 1200-1600rpm full boosts, 16-17psi(compared to 12-14psi of a stock T-25 on a DSM) and it will last longer. A friend of mine has a DSM w/a ball-bearing T-03 running 12's...nice car, he HAD a T-03 Mutt turbo running sleeve bearings and he ran a 13.6....can't take a HP number though, until recently there haven't been any AWD Dyno's in the area.

Not true, cars have waste gates that open to let exhaust by when you don't need it....so the turbo spool's down. 18-wheelers actuate the wastegate based on gear, not throttle, so there is no need to worry with them...but for us throttle controlled cars you have to wait...


Friction is the number 1 cause of lag, turbo's arn't all that big, even the HUGE one's. And the amount of exhaust going thru should allow quicker spools than is available on a sleeve type turbo.

Michael

RedRotaryRocket

N1XRR,

I think your concept of wastgate operation is a little fuzzy. They only open under boost, after you have reached your desired boost level. Cruising at 1500 RPM (or cruising at any RPM for that matter), the wastegate should be shut tight....that is if it's working correctly.

wakeech

are you really really sure that mass plays no role in it??
hey, i'm not pretending to be a big expert, but estimating the amount of rotational energy in that sucker at 100 000 rpm (i know they don't make much boost at 20 000 rpm, i'd just hate to think about running a "sleave" bearing, thanks, that fast) a gram would make a big difference in how fast it'd spool...??

and if mass isn't a determining factor, why do tuners trim the vanes, and/or undersize turbines (or oversize housings... whichever)??

RedRotaryRocket

Wakeech,

Mass of the turbo is still an important factor in spool up, regardless of what type of bearing is used. But yes, even the sleave bearing type turbos spin in excess of 100,000 RPM...crazy isn't it? :D

Sputnik

Then there wouldn't be much of a difference in lag between smaller and bigger turbos, would there? The bigger turbo is designed to pump more air into the engine, and it normally takes more exhaust to drive the turbo. So the bigger the turbo is, the longer it takes to get enough exhaust gasses going to get it up to speed (among other things, of course).

---jps

N1XRR

Note QUITE what I mean here...you have to compare apples to apples.

Take a T-25 and a T-03 sleeve bearing type and compare spool. Then take a T-25 and T-03 ball bearing type and compare spool. Sorry for the confusion.

Michael